Method and sheet assembly for producing imaged transparencies suited for projection

ABSTRACT

A sheet assembly for producing an imaged transparency comprises a donor sheet with a transferable coloured coating and a transparent image-receiving sheet with an auxiliary coloured coating, said two sheets being adapted to be disposed with their coatings in face-to-face contact for imagewise transfer of parts of the transferable coating from the donor sheet to the auxiliary coating of the image-receiving sheet.

United States Patent 11 1 Svensson 1 Oct. 8, 1971 [54] METHOD AND SHEET ASSEMBLY FOR 3,065,099 11/1962 Newman 117/361 PRODUCING IMAGED TRANSPARENCIES f; gar/man 17/36 7 ewman SUITED FOR PROJECTION 3,185,086 -5/l965 Ritzerfeld et al. 101/469 [76] Inventor: Karl Gunnar Svensson, Selma 3,370,170 2/1968 Gold 117/367 Lagerlofsvag 18 c, 682 00 Filipstad, 3,394,042 7/1968 Wingert et a1. 117/367 Sweden 3,637,414 1/1972 Newman 117/361 22 Filed: July 29,1971 Th 1 OTHEIE PUBLISATIONZ d 'e Pastic Coating orp., l 69, A ui e to Over- [21] Appl 167l31 head Projection, page 79.

[30] Foreign Application Priority Data Primary EXamiKlerDa/id Klein Aug. 17, 1970 Sweden 11169/70 Assistant Examiner-hm Goodmw Feb. 23, 1971 Sweden 2278/71 [57] ABSTRACT [52] US. Cl l17/36.1, 117/ 17.5, 101/469, A sheet assembly for producing an imaged transpar- 101/471 ency comprises a donor sheet with a transferable Co [51] Int. Cl B4lm 5/00 loured coating and a transparent image-receiving [58] Field of Search 117/367, 36.1, 36.2; sheet with an auxiliary coloured coating, said two l01/l49.4, 472, 469, 471 sheets being adapted to be disposed with their coatings in face-to-face contact for imagewise transfer of [5.6] References Cited parts of the transferable coating from the donor sheet UNITED STATES PATENTS to the auxiliary coating of the image-receiving sheet. 3,054,692 9/1962 Newman et al 117/175 3 Claims, 5 Drawing Figures METHOD AND SHEET ASSEMBLY FOR PRODUCING IMAGED TRANSPARENCIES SUITED FOR PROJECTION For education or demonstration purposes it is often desired to have the possibility of rapidly and cheaply producing an imaged transparency suited for subsequent use in a projector, particularly in a so-called overhead projector to provide an enlarged image on a projection screen.

There are several sheet assemblies available on the market for producing the imaged transparency. These sheet assemblies comprise a donor sheet which consists of a support sheet and a resinous, gluey, oily and/or waxy transferable layer anchored to the support sheet and containing colouring matter, and in contact therewith a transparent image-receiving sheet which is capable of engaging the transferable layer by picking it up in selected areas. There are various methods of transferring parts of the transferable layer from the donor sheet to the image-receiving sheet in order to produce on said image-receiving sheet an image so that said image-receiving sheet can then be used in the (overhead) projector as a transparency sheet. The prior art sheet assemblies suffer from several drawbacks. One drawback of most sheet assemblies is that the image produced on the image-receiving sheet lacks sharpness and clarity. Another drawback is that the transferred parts of the transferable layer of the donor sheet become poorly anchored to the image-receiving sheet. A further and essential drawback is that the image projected onto the projection screen will get so lucid and dazzling background portions that they cause considerable discomfort to the spectator, and moreover the projector operator becomes exposed to considerable eye strain and discomfort by stray reflected light from the overhead projector. To eliminate the latter drawback a separate colour filter has hitherto been placed in the path of the rays in the projector, which involves additional work and inconvenience when using the projector.

The present invention has for its object the elimination of the above drawbacks in an inexpensive and simple manner.

The invention thus provides a sheet assembly for pro ducing an imaged transparency for projection purposes, comprising a first support sheet, a transferable layer anchored to one face of said first support sheet and consisting of colouring matter and a material of the group consisting of resinous, gluey, oily and waxy matters, said first support sheet and said transferable layer forming a donor sheet of the assembly, a transparent second support sheet, and a transparent auxiliary layer anchored to one face of said second support sheet and consisting of colouring matter and a material of the group consisting of resinous, gluey, oily and waxy matters, said second support sheet and said auxiliary layer forming a transparent image-receiving sheet of the assembly, said donor sheet and said image-receiving sheet being adapted to be disposed with their said layers in face-to-face contact for imagewise transfer of parts of said transferable layer from said donor sheet to said auxiliary layer of said image-receiving sheet.

By providing the image-receiving sheet with an auxiliary layer of the above mentioned type it is realized that the transferable layer portions transferred to the imagereceiving layer will be well anchored and give an image of improved sharpness and clarity, and that the auxiliary layer filters the light of the projector in such a way that neither the projector operator nor the spectators are exposed to dazzling or eye straining scattered or reflected light.

It is suitable in many cases that the transferable layer of the donor sheet consists of a per se known pressuresensitive so-called contact carbon transferable layer. in such a case the invention is suited for production of the imaged transparency directly by the impact or pressure exerted by a pencil, pen or typewriter type or in print- It is suitable in other cases that the transferable layer of the donor sheet consists of a per se known thermographic transferable layer. In such a case the sheet assembly according to the present invention is utilized for the production of the imaged transparency by thermographic printing of a graphic original having image area portions surrounded by background portions, said image area portions having a greater capability than the background portions of absorbing radiatingenergy and thus of being heated. The graphic original is placed on the donor sheet, and the assembly of graphic original, donor sheet and image-receiving sheet is irradiated with radiating energy, the image area portions of the original thereby being heated and imagewise transferring heat by conduction to the donor sheet so that the transferable layer thereof, which engages the auxiliary layer of the image-receiving sheet, is heated in the portions corresponding to the image area portions of the original and in these portions release their anchorage to the support'sheet of the donor sheet and are transferred to the auxiliary layer of the image-receiving sheet and are anchored there.

in the last mentioned embodiment it may be suitable for the thermographic transferable layer to contain hectographic dyes so that the image transparency thermographically produced by means of the sheet assembly can be used for the double purpose of first producing in conventional manner a number of hectographic copies by a spirit duplication process and then being utilized in the projector.

The use of a sheet assembly for thermographic printing on the auxiliary layer provided on the imagereceiving sheet shall be characterized by two features: (I) the auxiliary layer contains a colouring matter which is substantially not heated when exposed to radiating energy but still-absorbs visible radiation to such an extent that it eliminates any strain of the eyes of spectators viewing the projection screen and also of the projector operator, and (2) the melting point and the tack point of the-auxiliary layer are higher than the melting point and the tack point of the transferable layer of the thermographic transfer sheet and the melting point of the auxiliary layer is higher than the temperature at which the thermographic tiarisfer takes place.

, Comprehensive experiments have shown that excellent results are obtained under the following conditions, which individually and all in combination contribute to favourable results. The transferable layer of the donor sheet thus is preferably but not necessarily disposed on a polyester support film to which the transferable layerv is very well anchored at room temperature although the anchorage will be lost to a large extent at 60 to C,'above which temperature the thermocopy transfer takes place. The transferable layer preferably has a melting point of about 76C and is applied on the support sheet of the donor sheet in an amount of about to l l g/sq.m., preferably 8 g/sq.m. The receiving waxy auxiliary layer on the image-receiving sheet has a weight of 2 to 5 g/sq.m., preferably 3 g/sq.m., and a melting point of 80 to 90C or even higher, preferably 86C, and a tack point which is several degrees lower. The thermoprinting temperature employed lies betwen the tack point of the transferable layer of the donor sheet and the melting point of the auxiliary layer of the image-receiving sheet, and at such a thermocopying temperature the transferable layer of the donor sheet is firmly anchored to the auxiliary layer of the imagereceiving sheet without reducing the bond or anchorage between the support sheet and auxiliary layer of the image-receiving sheet.

The invention will be more fully described hereinbelow with reference to the accompanying drawings and working examples.

In the drawings:

FIG. 1 shows an enlarged cross section of one embodiment of a sheet assembly according to the invention when a thermographic reflex copying process is utilized;

FIG. 2 shows in a similar manner a second embodiment of a sheet assembly according to the invention with the use of a thermographic transmission printing process;

FIG. 3 shows a cross section of a sheet assembly comprising a donor sheet and a transferable layer of the contact carbon type; I

FIG. 4 corresponds to FIG. 3 but also shows an auxiliary sheet placed on the sheet assembly; v

FIG. 5 shows a cross section of the sheet assembly in FIG. 3 after pressure has been applied thereto whereafter the sheets have been separated slightly.

In FIG. 1, 1 is a graphic original with image portions 2 which are surrounded by background portions and have a greater capability than said background portions of absorbing radiating energy and thereby being heated. 3 designates a donor sheet which consists of a support sheet 4 and a transferable layer 5 which absorbs light more or less. A transparent image-receiving sheet 6 consists of a light absorbing auxiliary layer 7 having a high tack point which is coated on a support sheet 8. This support sheet 8 can be made from several types of transparent film material but especially film of polyester has particularly reliable properties. The auxiliary layer 7 which shall also be transparent and contain colouring matters preferably of low capability of being heated by absorption of radiating energy, shall be resinous, gluey. oily and/or waxy to be able to anchor the transferable layer 5 to itself during the thermographic copying described in the following.

In the thermographic transfer process according to FIG. I the uppermost surface, that is, the support sheet 8 of the image-receiving sheet faces the source of radiating energy. If the graphic original is imaged only on one face and the background areas can be penetrated by radiating energy without being heated, it is also possible to place the source of radiating energy on the opposite side of the assembled sheets, particularly if a surface 9 reflecting radiating energy is positioned beneath and in contact with the support sheet 8, as shown in FIG. 2.

Example 1 indicates a suitable composition of the auxiliary layer 7.

Example I Waxes 60-90% resins 0-l0% lubricants 25% fatty alcohols 0.5-7.0% fatty acids 00.7% surfactants l-5% organic solvent not volatile or slightly volatile at the thermocopying temperature and having one or more OH-groups O 5-8'7r dyes l-8% Suitable waxes are of the type used in the manufacture of carbon paper.

The resins which are intended to give the composition suitable tackiness, can be natural or synthetic.

Suitable dyes should have a low capacity of being heated by absorption of radiating energy and may be of the oil soluble or spirit soluble type or be basic dyes. Dyes which are considerably heatable by absorption of radiating energy, such as dyes of the nigrosin or indulin type, offer no advantages but would contribute to pro.-

ducing a non-desirable lack of contrast in the image to be projected, and the background portions of the image would appear unclean unless a very low content is used, that is, so low a content that it would be difficult to control.

Dyes usually employed in hectographic master sheets, such as basic dyes, should be used sparingly and only to assist in obtaining a pleasant colour hue of the auxiliary layer.

The solvent of the described type, as well as the fatty alcohol, assists in making the solution of the dye complete and stable. Such solvents as glycols are simultaneously useful as aids in keeping the image-receiving sheet flat even when it is exposed to the heat prevailing in the beam of rays in the projector.

Example 2 A composition which has proven suitable is indicated hereinbelow. A mixture of OP-Wachs and KP-Wachs The composition withstands the duplicating liquid in spirit duplication without serious deterioration of the mechanical and physical (optical) properties.

Within the scope of the invention, great variations of thecomposition of the auxiliary layer 7 are permissible. It has also proven suitable to provide the auxiliarylayer by printing in a printing press by means of a transparent printing ink. Many inks suitable for this purpose are commercially available.

The sheet assembly shown in FIG. 3 comprises a donor sheet 11, 12 which is placed on an image receiving sheet 13, 14. The donor sheet consists of a support sheet 11 and a transferable layer 12 anchored to one face of the support sheet. The image-receiving sheet which is transparent consists of a support sheet 14 and an auxiliary layer 13 anchored to one face thereof. The donor sheet and the image-receiving sheet are superimposed, with the layers 12 and 13 adjacent to and in contact with one another.

The transferable layer 12 of the donor sheet 11 is a resinous, gluey or waxy pressure-sensitive contact carbon transferable donor layer. Such transferable layers are previously known in various compositions and hereinafter only a few examples are given of the possible composition of such donor layer. Such a contact carbon transferable donor layer has the property, as distinct from the transferable layers of ordinary pressure-sensitive carbon papers, that when exposed to a printing pressure, e.g., by means of a pen, pencil or in a typewriter, or printing press, it will not produce any markings on an underlying ordinary paper but provides such markings on a paper, the surface of which has been made receptive for instance by means of a receiving layer. The auxiliary layer 13 of the image-receiving sheet is of just such a nature that the transferable layer 12 can provide markings thereon under the action of printing pressure, whereas the transferable layer 12 would not give any markings on the support sheet 14 of the image-receiving sheet if the auxiliary layer 13 were missing. The support sheet 14 and the auxiliary layer 13 of the image-receiving sheet are suitably of the type described in conjunction with FIGS. 1 and 2.

When the sheet assembly according to FIG. 3 is to be used in order to obtain an imaged sheet suited for projection, a printing pressure by means of a typewriter, printing press, pen, pencil or like element is exerted locally on the upper side of the support sheet 11 corresponding to a desired image or text, so that the transferable layer 12 is locally pressed imagewise against the auxiliary layer 13 and adheres thereto. The printing pressure is suitably exerted against the support sheet 11 in such a way that an imagewise marking 16 (FIG. 5) is obtained also on the sheet 11. Upon subsequent separation of the donor sheet 11, 12 and the imagereceiving sheet 13, 14 as will appear from FIG. 5, portions 18 of the transferable layer 12 will remain imagewise on the auxiliary layer 13, and corresponding interstices 17 will form in the transferable layer 12 on the sheet 11 opposite its markings 16. The image-receiving sheet 13, 14 with the transferable layer portions 18 anchored thereto constitute an image transparency sheet which is immediately useful for projection purposes in an overhead projector. The auxiliary layer 13 on the image transparency sheet 14, 13, 18 contains a colouring matter which is substantially not heated when exposed to radiating energy although it will absorb visible radiation to such an extent that it eliminates any fatigue of the eyes of a spectator viewing the overhead projection screen and eliminates stray light from the object table of the projector, which is so discomforting to the projector operator. The transferable layer portions 18 of the image transparency contain pigments or dyes sufficiently absorbing or altering the projector light impinging on the transferably layer portions 18 so that a projection image of a high contrast is obtained.

In some cases, for instance when the support sheet 11 is a film, the free face of which is untreated and glossy and therefore not particularly well suited to receiving print by means that exert printing pressure, such as pens, pencils, printing presses or typewriters, it may be suitable to apply, in accordance with FIG. 4, on top of the support sheet 11 an auxiliary sheet 15 which consists of a tracing film or a transparent tracing paper, on which the markings can be obtained with the aid of the means that exert printing pressure. The sheet 15 can also be for instance a finished drawing which is easily copied by tracing. The sheet assembly according to FIG. 4 is used in the same manner as the sheet assembly according to FIG. 3 except that the markings 16 (FIG. 5) are obtained on the sheet 15 instead of the support sheet 11.

Paper or film of optional material with or without surface lacquering or surface roughening can be used as a support sheet 11. As already mentioned, the transferable layer 12 shall be made in a known manner as a contact carbon transferable layer. This layer 12 can preferably be realized by solvent coating with for instance trichloroethylene as solvent according to the following example:

Trichloroethylene parts by weight resin 2 do. do. do. lithopon 25 do. do. do. black pigment (black lake) 8 do. do. do.

Instead of the 8 parts of black pigment another example has 2 parts by weight of carbon black and 6 parts by weight of clay. As resin, use can be-made of a natural resin, such as WW resin or a synthetic resin. Also a white or other than black pigment can be used instead of the black pigment. The important thing is that the transferable layer such as it is deposited as markings 18 (FIG. 5) on the image-receiving sheet 13, 14 absorbs light considerably better or in another hue than the sheet 13, 14 proper to provide a projected image of high contrast on a projection screen.

The advantages of the embodiment according to FIGS. 3 to 5 are numerous. Thus, it is not necessary to use special typewriter ribbons for typing directly on glossy film. Such ribbons are difficult to'produce and generally give an irregular and deficient adherence and therefore an easily smudged print. Moreover, without access to equipment for thermocopying or duplicating it is possible to produce directly a finished imaged transparency ready for immediate use. This imaged transparency is excellently storageable without any risk of damage or deterioration by careless handling. This imaged transparency is entirely smudge-proof, which is of great importance because smudging, if any, of the object table of the projector, which usually is a large plate of clear glass, is to be considered a serious inconvenience in that it reduces the readiness for use of the projector and makes it more difficult to maintain in a neat and clean condition. Furthermore, the imaged transparency is of such a type that neither the eyes of the projector operator nor those of the spectators are exposed to dazzling, harmful or discomforting stray light, and this is attained without the necessity of providing separate filters.

1. In a sheet assembly for producing an imaged transparency for projection purposes from a graphic original having image portions and background portions, comprising a first support sheet, a transferable layer anchored to one face of said first support sheet and consisting of colouring matter and a material of the group consistingof resinous, gluey, oily and waxy matters, said first support sheet and said transferable layer form- What I claim and desire to secure by Letters Patent ing a donor sheet of the assembly, a transparent second support sheet, and a transparent auxiliary layer anchored to one face of said second support sheet and consisting of a material of the group consisting of resinous, gluey, oily and waxy matters, said second support sheet and said auxiliary layer forming a transparent image-receiving sheet of the assembly, said donor sheet and said image-receiving sheet being adapted to be disposed with their said layers in face-to-face contact for imagewise transfer of parts of said transferable layer from said donor sheet to said auxiliary layer of said image-receiving sheet, the improvement consisting in that colouring matter having low capability of being heated by absorption of radiation energy is incorporated into said transparent auxiliary layer in even distribution.

2. A sheet assembly according to claim 1 in which said auxiliary layer is of the following composition:

wax 60-90 percent resin -lO do. lubricant 2-5 do. fatty alcohol 0.5-7.0 do. fatty acid 0-O.7 do. surfactant 1-5 do. organic solvent, substantially non-volatile below 70C and v containing a number of OH-groups 0.58 do. dye 1-8 do.

3. In a sheet assembly for producing an imaged transparency for projection purposes from a graphic original having image portions and background portions, comprising a first support sheet, a pressure transferable 8v layer anchored to one face of said first support sheet and consisting of colouring matter and a material of the group consisting of resinous, gluey, oily and waxy matters, said first support sheet and said transferable layer forming a donor sheet of the assembly, a transparent second support sheet, and a transparent auxiliary layer anchored to one face of said second support sheet and consisting of a material of the group consisting of resinous, gluey, oily and waxy matters, said second support sheet and said auxiliary layer forming a transparent image-receiving sheet of the assembly, said donor sheet and said image-receiving sheet being adapted to be disposed with their said layers in face-to-face contact for imagewise pressure transfer of parts of said transferable layer from said donor sheet to said auxiliary layer of said image-receiving sheet, the improvement consisting in that colouring matter having low capability of being heated by absorption of radiation energy is incorpo-' v UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. ,386 Dated October 8, 1974 lnventofls) Karl Gunnar Svensson It is certified that error appears in the above-ifientified patent and that said Letters Patent are hereby corrected as shown below:

[451' "90. 8, 1971" should read Oct. 8, 1974 Signed and sealed this 21st day of January 1975.

(SEAL) Attest: I

MCCOY M. GIBSON. JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM'DC 60376-PB9 U.S. GOVEFNMENT PRINTING OFFICE 869. 93 o 

1. IN A SHEET ASSEMBLY FOR PRODUCING AN IMAGED TRANSPARENCY FOR PROJECTION PURPOSES FROM A GRAPHIC ORIGINAL HAVING IMAGE PORTIONS AND BACKGROUND PORTIONS, COMPRISING A FIRST SUPPORT SHEET, A TRANSFERABLE LAYER ANCHORED TO ONE FACE OF SAID FIRST SUPPORT SHEET AND CONSISTING OF COLOURING MATTER AND A MATERIAL OF THE GROUP CONSISTING OF RESINOUS, GLUEY, OILY AND WAXY MATTERS, SAID FIRST SUPPORT SHEET AND SAID TRANSFERABLE LAYER FORMING A DONOR SHEET OF THE ASSEMBLY, A TRANSPARENT SECOND SUPPORT SHEET, AND A TRANSPARENT AUXILIARY LAYER ANCHORED TO ONE FACE OF SAID SECOND SUPPORT SHEET AND CONSISTING OF A MATERIAL OF THE GROUP CONSISTING OF RESINOUS, GLUEY, OILY AND WAXY MATTERS, SAID SECOND SUPPORT SHEET AND SAID AUXILIARY LAYER FORMING A TRANSPARENT IMAGE-RECEIVING SHEET OF THE ASSEMBLY, SAID DONOR SHEET AND SAID IMAGE-RECEIVING SHEET BEING ADAPTED TO BE DISPOSED WITH THEIR SAID LAYERS IN FACE-TO-FACE CONTACT FOR IMAGEWISE TRANSFER OF PARTS OF SAID TRANSFERABLE LAYER FROM SAID DONOR SHEET TO SAID AUXILIARY LAYER OF SAID IMAGE-RECEIVING SHEET, THE IMPROVEMENT CONSISTING IN THAT COLOURING MATTER HAVING LOW CAPABILITY OF BEING HEATED BY ABSORPTION OF RADIATION ENERGY IS INCORPORATED INTO SAID TRANSPARENT AUXILIARY LAYER IN EVEN DISTRIBUTION.
 2. A sheet assembly according to claim 1 in which said auxiliary layer is of the following composition:
 3. In a sheet assembly for producing an imaged transparency for projection purposes from a graphic original having image portions and background portions, comprising a first support sheet, a pressure transferable layer anchored to one face of said first support sheet and consisting of colouring matter and a material of the group consisting of resinous, gluey, oily and waxy matters, said first support sheet and said transferable layer forming a donor sheet of the assembly, a transparent second support sheet, and a transparent auxiliary layer anchored to one face of said second support sheet and consisting of a material of the group consisting of resinous, gluey, oily and waxy matters, said second support sheet and said auxiliary layer forming a transparent image-receiving sheet of the assembly, said donor sheet and said image-receiving sheet being adapted to be disposed with their said layers in face-to-face contact for imagewise pressure transfer of parts of said transferable layer from said donor sheet to said auxiliary layer of said image-receiving sheet, the improvement consisting in that colouring matter having low capability of being heated by absorption of radiation energy is incorporated into said transparent auxiliary layer in even distribution. 